Does the seatbelt on your 2000-present Ford, Lincoln or Mercury product retract lazily or not at all when unbuckled? Ford Technical Service Bulletin (TSB) 05-16-11 has details on a kit the dealership can install to improve retraction speed. Teflon tape is used to reduce friction in the seatbelt assembly.

Does your 2000-05 Taurus, Windstar or Freestar/Monterey/Sable leak around the transaxle dipstick? Does the dipstick give inconsistent readings when you check the oil? There's a rubber disc inside the transaxle vent, meant to keep water out, that can stick and cause improper venting. TSB 05-14-5.

Moonshine?

Q: I'm suspicious that the local cut-rate gas station's premium gas isn't what it's represented to be. My BMW seems to run fine on it, but the Check Engine light comes on right after I fill up there. And if I fill up with premium anywhere else, the light goes out. My wife's minivan seems to run fine on their regular grade. I hate to pay close to 40 cents extra for premium at the branded station across the street. Is this damaging my engine, and how can I tell if there's something wrong with the gasoline?

JOHN BOGARTES

SUFFOLK, NY

A:Any mechanic with a scan tool can tell you why the Check Engine light is on. There are even simple consumer-grade code checkers you can buy for a street price under $75. For a couple of hundred, you can get a scanner and actually see engine parameters changing in real time.

Is this gasoline damaging your engine? Probably not, because if the octane rating is too low, the engine computer will roll back the timing to prevent engine knock and, possibly, melted pistons. However, if the fuel has been adulterated with something else, there may be damage to the fuel system. The common adulterant is alcohol. Alcohol will raise the octane rating of gasoline, but at the expense of fuel economy. I've seen both ethanol and methanol used to dilute gasoline. Ethanol used to be employed in concentrations as high as 10 percent to formulate oxygenated fuel. At one time such fuel was mandated by the EPA in some areas during months when there were high carbon monoxide levels in the atmosphere. This small amount and concentrations of methanol as high as 0.3 percent are acceptable, and specifically permitted by most of the car manufacturers. Higher concentrations in vehicles not designed for alcohol can cause corrosion of metal parts wetted by fuel--things like the inside of the tank and the lines, and the pintle valve in the injectors. High concentrations of alcohol also can make non-alcohol-rated plastic parts turn to Jell-O in a few months. I'm aware of at least two well-publicized prosecutions of individuals who were caught selling tank cars full of methyl alcohol under the table to unscrupulous gas station owners and fuel distribution brokers.

How to tell if you're trying to burn alcohol-bearing gasoline? Here is some simple kitchen-table chemistry. Get a tall, skinny vessel and add a measured amount of ordinary ethylene-glycol-based antifreeze to it. Fill to a level you can check easily, even if it's just a grease pencil mark. The vessel should be about one-third full. Sight to the bottom of the meniscus, not the high point where the liquid wets the wall. Add a similar amount of your suspect gasoline. Cover the top of the vessel and invert it carefully about a dozen times. Do not shake. Allow the mixture to stand for an hour or so to let the bubbles coalesce. Any alcohol--methyl or ethyl--will migrate to the glycol layer on the bottom. If the meniscus stays at the same level, you have pure gasoline. If the meniscus goes up about 10 percent, you have legal oxygenated fuel. If it goes up more than 10 percent, you have adulterated fuel. Be sure to dispose of your gasoline-alcohol-antifreeze highball in some environmentally responsible manner, okay? Check the Saturday Mechanic article in our December issue for details on that.

There are plenty of vehicles that use heater hoses with wacky bends molded into them, all the better to keep an errant hose from fouling something abusive, like the radiator fan or a red-hot exhaust manifold. Which is fine unless you're in Burnt Stump, Ark., and the hose busts open. Rather than take up temporary residence until the vehicle-specific premolded hose shows up, try using the E-Z Coil, a metal spring that will keep your hoses where they belong. It will soon be available wherever Goodyear products are sold. goodyear.com

Don't Touch That Dial

Q: I have a 2004 Envoy with the standard FM radio and a single-disc CD player. When I went to upgrade the player (with a non-GMC product), I was informed that the radio could not be removed or replaced as it controls the airbags. Is this true? Have you guys ever heard of anything so stupid? If so, is there a way around it? I wanted to do this as there are no GMC satellite/CD players with MP3 capability.

RICK BUTTON

VIA E-MAIL

A:The airbag system has its own dedicated wiring harness that has nothing to do with the rest of the truck's wiring or the radio. Maybe somebody is confused because the original radio has volume and station-changing controls built into the steering wheel, right where the pyrotechnics for the airbag live. The new radio may not be compatible with the airbag's components--but that won't affect the airbag operation.

High Voltage

Several years ago there was a lot of talk about the possibility of changing cars from 12-volt to 42- to 48-volt systems. Is it still under consideration or was it found to be infeasible? PM is really great for keeping me up-to-date concerning all the news of transportation innovations, which I do appreciate very much.

JOHN SALTER

JACKSON, MS

A:Yes, 42-volt electrical systems were supposed to be the wave of the future. Current automotive systems, which we call 12-volt, actually operate at about 14 volts, so the proposed 42-volt systems are triple this voltage. Most aircraft have operated at 28 volts for generations. The advantages to upping the voltage include reduced weight of wires, motors and actuators throughout the vehicle, as 12-volt parts need to be larger to carry enough current to get the job done. The conversion meant integrated generators and starters built into the flywheel, a/c systems with an electrically powered pump mounted anywhere except inside the engine compartment, and electric (not hydraulic) power steering.

Didn't happen, isn't gonna happen. Why? Seems the industry couldn't make 42-volt systems as reliable as they thought they could. Switching AC is easier because the voltage passes through zero volts 120 times a second. DC voltage is constant, and simply yanking a switch open starts an arc that rapidly degrades the metal contacts. At 12 to 14 volts, the arc is small enough not to be an issue. But at 42 volts, the erosion of the contacts shortens life span too much. Switch contacts can be upgraded and electronically protected from this--but it all costs money. Soon we'll have 300-volt hybrid systems in many cars, and we can tap this voltage for things like the starter and air conditioning. Also, many vehicles now have multiplexed wiring using one wire to operate several devices. This reduces the weight and volume of the harness substantially.

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